The seeds of House Majority Leader Eric Cantor's shocking primary loss may have been sown in January.

That's when House Republican leaders insisted on floating a set of immigration principles at the party's retreat as a gesture toward acting on the Senate Gang of Eight immigration bill. The principles were shelved, but they stoked the worst fears of opponents of the Gang of Eight bill - that no matter how dead the bill seemed, it could be revived instantly.

The principles helped keep the issue alive, and in so doing, lit the long fuse on the stick of dynamite that ignited in Virginia's 7th Congressional District.

Eric Cantor wouldn't be on the top of anyone's list of victims of an immigration backlash. He's not John McCain or Lindsey Graham. His offense was speaking in favor of an unspecified version of the DREAM Act and making occasional favorable sounds about more far-reaching legislation.

The standard for convicting Cantor, it turns out, wasn't guilt beyond a reasonable doubt, or preponderance of evidence. It was simple suspicion. Conservatives suspected that the House leadership wanted to pass immigration reform, no matter what it might say, and suspected that Cantor would be part of it, no matter what he might say. The message of the district's primary voters on immigration was, "We don't trust you."

There are few issues in American life that so justify a thoroughgoing cynicism as immigration. The political elite has never cared about enforcing immigration laws; it invariably sells whatever is the latest version of "comprehensive" reform in dishonest terms; and it has an ill-disguised contempt for the alleged boobs who take immigration enforcement seriously.

Of course, Cantor couldn't have possibly lost, let alone lost by double digits, if he wasn't vulnerable more broadly. Compared with his underfunded, underdog opponent, Cantor was the well-heeled Big Dollar candidate, the powerful Inside Washington candidate, the highly connected Big Business candidate. In most circumstances, these are formidable strengths, but David Brat used them against Cantor in an act of populist jujitsu.

The insurgent candidate's opposition to amnesty was part of a larger anti-Washington and anti-Wall Street working-class message. Brat constantly linked immigration to jobs and wages. In his closing argument, he said, "Cantor continues to work with multinational corporations to boost the inflow of low-wage guest workers to reduce Virginians' wages and employment opportunities." He attacked the Chamber of Commerce and the Business Roundtable. He tweeted out a picture of Cantor posing with Facebook founder Mark Zuckerberg - an enthusiast for the importation of more foreign workers - with the caption "Eric Cantor doesn't represent you."

In a nutshell, Brat took a version of the populist conservatism championed by Alabama Sen. Jeff Sessions (and the influential, Brat-supporting talk-show host Laura Ingraham) and weaponized it against Cantor. It proved incredibly powerful.

The Brat message is one that all Republicans should heed. If the GOP is ever going to become identified as the pro-worker party again, it must oppose flooding the labor market with new, wage-suppressing foreign labor at the behest of business interests. But obviously this can't be the entirety of the Republican agenda. The irony is that Cantor has been one of the Republicans trying to fill in the rest of the picture with a bread-and-butter economic agenda aimed at ordinary workers.

Indeed, Eric Cantor's contributions to the party have been considerable. He rose in the House as a young reformer when the House Republicans had a literally corrupt establishment. A tireless party-builder and committed (if realistic) conservative, he did much to nurture the Republican candidates who took the House in 2010.

If he and other members of the leadership had unmistakably slammed the door on the Gang of Eight bill or any permutations of it, he would probably still be on his way to the speakership. Now, the bill is dead, and so is his House career.